Carbon Baking Furnace

ABSTRACT

A carbon baking furnace has at least one vertical baking shaft with a system and method for positioning green carbon bodies to be baked at the top of the vertical baking path and ringing the green carbon bodies with a sacrificial medium such as packing coke. The disclosure provides a system and method for controlling the delivery and removal of the sacrificial medium used to surround the carbon bodies within the baking paths. A volatile extraction system and method are provided. A system and method for unloading baked carbon bodies is disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application claiming priority to U.S.patent application Ser. No. 14/436,182 filed Apr. 16, 2015, which is aUnited States National Stage Patent Application filed under 35 U.S.C. §371 claiming priority to PCT/IB2013/002317 having an internationalfiling date of Oct. 16, 2013, which application claims the benefit ofU.S. Provisional Patent Application 61/714,634 filed Oct. 16, 2012.

BACKGROUND OF THE DISCLOSURE 1. Technical Field

The present disclosure generally relates to carbon baking furnaces and,more particularly, to carbon baking furnaces having vertically-disposedbaking paths. In one configuration, the invention relates to a furnacehaving at least one, but typically an array of vertically-disposedbaking paths used to bake a carbon body that travels down through thebaking paths while packed in a sacrificial medium.

2. Background Information

Various operations require green carbon to be baked prior to use. Someof these operations use granulated green carbon while others use blocksof green carbon. One such baking operation is the manufacture of anodesthat are later used to make aluminum. The conversion of alumina toaluminum metal by electrolysis results in the substantial consumption ofcarbon anodes. Molten aluminum is deposited onto a carbon cathode andsimultaneously oxygen is deposited on and consumes the carbon anode ofthe electrolytic cell. Typically, up to 0.4 tonnes of carbon areconsumed for every tonne of aluminum produced. As a result, aluminumsmelters have a requirement for a substantial and continuous supply ofcarbon anodes. Smelters commonly manufacture carbon anodes on site as anintegral part of the aluminum production process.

The manufacture of carbon anodes for the aluminum manufacturing processincludes producing “green” anode blocks and baking the “green” blocks toproduce anodes suitable for use in the aluminum manufacturing process.The production of “green” blocks involves the mixing of crushed coke oranthracite with a binding agent which, for example, contains coal tarpitch. The viscous mixture is then pressed to form “green” anode blocks.Depending on the smelter's requirements, “green” anodes may typicallyweigh from a few hundred kilograms to more than a tonne. The mixture ofcoke and pitch binder is generally solid at room temperature and softensat temperatures over about 50 degrees C. Volatile components arereleased at temperatures between 50 degrees C. and 400 degrees C. Whensubjected to further heating over a period of time, to about 1200degrees C., the anode hardens, resulting in improved physicalproperties, such as electrical conductivity and resistance to oxidation.

A carbon anode baking furnace having a substantially vertical bakingpath is disclosed in WO 99/06779. Green anodes are packed in sacrificialmedia within the vertical baking path and moved downwardly through abaking zone. The baked anodes are removed from the bottom of the bakingpath along with a portion of the sacrificial medium that surrounds theanodes. The movement of the sacrificial medium within the baking pathmust be controlled such that the removal of the bottom anode does notupset the packing of the sacrificial medium about an anode disposedhigher up the baking path. The loading and unloading of the sacrificialmedium is an issue desirous of improvement.

Another issue with the vertical-path furnace such as that disclosed inWO 99/06779 is the removal of the baked anodes at the bottom of thefurnace. The anodes are disposed in a self-supporting column while inthe baking path. The problem of removing the lowermost baked anode whilenot upsetting the column is an issue desirous of improvement.

The removal and treatment of pitch fumes or volatiles is an issuedesirous of improvement.

SUMMARY OF THE DISCLOSURE

The disclosure provides a carbon baking furnace having at least onevertical baking shaft with a system and method for positioning greencarbon bodies to be baked at the tops of the vertical baking paths andringing the green carbon bodies with a sacrificial medium such aspacking coke.

The disclosure provides a carbon baking furnace having at least onevertical baking shaft with a system and method for controlling thesacrificial medium used to surround the carbon bodies within the bakingpaths. The system and method includes elements disposed at the top ofthe furnace where the sacrificial medium is loaded and elements disposedat the bottom of the furnace where the sacrificial medium is unloaded.

The disclosure provides a carbon baking furnace having a system andmethod for unloading baked carbon bodies at the bottom of an array ofbaking paths while supporting the column of carbon bodies remaining inthe baking path.

The disclosure provides a volatile extraction system that extractsvolatile fumes from the upper portion of the furnace and introduces thevolatile fumes to the burners in the baking portion of the furnace. Thissystem allows the volatile fumes to be selectively directed to anafterburner and automatically delivered to the afterburner during anemergency.

The disclosure provides volatile extraction channels that areindependent of the baking fume channels and are sandwiched betweenportions of the baking fume channels.

The disclosure provides volatile extraction inlets that are slopedupwardly from the baking paths.

The disclosure provides a sacrificial medium delivery system havingchannels to deliver medium to the baking path.

The disclosure provides grab assemblies that pinch and hold the secondlowermost article to allow the lowermost article to be removed from thefurnace.

The disclosure provides methods of using associated with each of thesystems of the furnace.

The disclosure will now be further described with reference to theaccompanying drawings. In the drawings the carbon articles arerepresented by anodes for use in the aluminum smelting industry. It willbe understood that the features of the present invention applies equallyto the baking of other carbon articles provided in block or granularform.

The plurality of individual furnace features and method steps describedin this disclosure may be combined with one another to form additionalunique combinations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an exemplary configuration of a vertical-pathcarbon baking furnace having a plurality of baking paths arranged in anarray.

FIG. 2 is a top view of the exemplary furnace configuration of FIG. 1.

FIG. 3 is a perspective view of the top of the furnace showing sixanodes positioned at their uppermost position with two baking pathsempty for purposes of showing the structures around the top of thebaking path. FIG. 3 also shows the system for loading sacrificial mediuminto the baking paths around the anodes.

FIG. 4 is a perspective view of the top of a baking path with the anoderemoved to show the anode guides, the brushes, and the sacrificialmedium conveyors. This view also shows openings in the refractory blockthat define the inlets to the volatile fume removal system.

FIG. 5A is a section view through the furnace wall at the volatileextraction opening.

FIG. 5B is a perspective view of on configuration of a liner for avolatile fume extraction channel.

FIG. 5C is a schematic view of a segmented volatile extraction channelcontrolled with individual valves.

FIG. 6 is a perspective view from inside a baking path looking up to thetop of the baking path with the refractory block removed to show theoverlapping brushes and the outlets to the sacrificial medium conveyors.

FIG. 7 is a perspective view of the loading end of a sacrificial mediumconveyor used to deliver sacrificial medium to the top of the bakingpath around an anode.

FIG. 7A is a section view taken along line 7A-7A in FIG. 7 showing howthe supply of sacrificial medium may be controlled with an adjustabledoor.

FIG. 8 is a perspective view of the end of the sacrificial mediumconveyor of FIG. 7 showing the adjustment mechanism for the drive chain.

FIG. 9 is a perspective view of the sacrificial medium conveyor of FIGS.7 and 8 showing the brush and the outlet openings that allow thesacrificial medium to exit the conveyor into the baking path around theanode.

FIG. 10 is a top perspective view of a portion of the sacrificial mediumconveyor of FIGS. 7 and 8 showing an idler roller and a paddle that isused to distribute the sacrificial medium along the length of theconveyor.

FIG. 11 is a perspective view of six volatile extraction channels shownwithout the refractory brick and the selectively configurableconnections between these channels and the burners and afterburner.

FIG. 12 is a perspective view of the side of the furnace showing themain furnace burners and the pipes used to deliver the volatile fumes.

FIG. 13 is an end view of an exemplary sacrificial medium controlassembly that is disposed at the bottom of the baking path.

FIG. 14 is a schematic cross section of the sacrificial medium controlassembly showing the movement of the sacrificial medium with schematicarrows.

FIG. 15 is a perspective view of the end of the assembly shown in FIG.14 with the anode removed for clarity.

FIG. 16 is a perspective view looking up into the bottom of an anodebaking path showing the location of the structure of FIG. 15 and alsoshowing a typical actuation mechanism for the sacrificial medium controlassembly.

FIG. 17 is a perspective view of a portion of an exemplary conveyor usedto move baked anodes out from under the furnace after the baked anodehas been removed from the baking path.

FIG. 18 is a perspective view of a mechanism that unloads the lowermostbaked anode and controls the movement of an anode column through thebaking path.

FIG. 19 is a perspective view of the mechanism of FIG. 18 with portionsremoved to show additional features.

FIG. 20 is a perspective view looking up at one side of the bottom oftwo adjacent baking paths showing the holding devices that are used tosupport the anode column while the lowermost baked anode is removed fromthe furnace.

FIG. 21 is a schematic view showing an exemplary configuration for theholding devices and the actuators for the holding devices.

FIG. 22 depicts actuators for the holding devices that hold the anodecolumn during the unloading of an anode.

FIG. 23 is a side perspective view showing the holding devices of FIG.20 engaged with an anode while the lowermost baked anode is removed andalso depicting an alternative actuator for the holding devices.

FIG. 24 depicts a pair of holding devices disposed on a common driveshaft.

FIGS. 25 and 26 show two positions for an accommodating holder device.

FIG. 27 is a top schematic view of an alternative conveyor configurationfor unloading anodes.

FIG. 28 is an end view of FIG. 27.

FIG. 29 is a top view of an alternative anode spacer disposed on top ofan anode.

FIG. 30 is a side view of the furnace body showing the gas flowchannels.

FIG. 31 is a section view taken through FIG. 30 at the location a set ofvolatile extraction inlets.

FIG. 32 is a section view taken through the baking paths showing thearrangement of the volatile extraction inlets.

FIG. 33 is a section view through the furnace body showing the linersused with the volatile extraction inlets.

Similar numbers refer to similar parts throughout the specification.

DETAILED DESCRIPTION OF THE DISCLOSURE

An exemplary configuration of a vertical-path baking furnace isidentified by reference numeral 10 in the following description. FIG. 1depicts a front view of furnace 10 while FIG. 2 depicts a top view offurnace 10 showing the location of a plurality of carbon body bakingpaths 12 arranged in a three-by-four array with three baking path rowsand four baking path columns. The array of baking paths 12 thus includesa plurality (in this example ten) of perimeter baking paths that are notentirely surrounded by other baking paths and, in this example, aplurality (two) of captured baking paths 12 that are entirely surrounded(when viewed from the top) by other baking paths 12. The array of bakingpaths includes a front row 14 of baking paths 12, a middle row 16, and aback row 18. In other array configurations, there will be a differentnumber of middle rows 16 to increase the production capacity. In thisconfiguration, the front row is the closest to the unloading directionat the bottom of furnace 10. In FIG. 2, the baked carbon bodies areunloaded from the bottom of the baking paths 12 in the direction thatfaces the bottom of the drawing page which corresponds to the directiontoward the viewer in FIG. 1 (this is the front 20 of furnace 10). Thebaking paths 12 are generally rectangular and are larger than butgenerally the same shape as the carbon body that is to be passed throughthe baking path 12. In other configurations, the shape of the bakingpath 12 may differ from the shape of the carbon body. The size of thebaking paths 12 allow the carbon bodies to be surrounded by asacrificial medium such as granular packing coke. The sacrificial mediummay be any medium which will protect the carbon bodies during the bakingprocess. The sacrificial medium may preferentially react with or absorbthe oxygen in the furnace prior to its reaction with the carbon in thearticles being baked. It is preferred that the sacrificial medium befriable to permit it easy incorporation around the carbon articles andto permit the easy movement of the carbon articles within the kiln. Thesacrificial medium may be selected to provide an optimum balance ofrendering the carbon articles easily moveable through the furnace andproviding sufficient protection of the carbon articles from oxygencontained within the kiln. In one configuration, the sacrificial mediumhas a maximum particle size of less than fifteen millimeters.

Green carbon bodies 30 are loaded into baking paths 12 at the top offurnace 10 and unloaded at the bottom of furnace 10 where the bakedcarbon bodies 30 are unloaded from a bottom of a baking path 12. Theunloading process controls the downward movement of the carbon bodies 30through furnace 10 during the baking process such that each verticalcolumn 32 of carbon bodies 30 is supported from the bottom. Carbonbodies 30 move through furnace 10 in a substantially continuous mannerand the time for a single carbon body 30 to move through baking path 12is many hours. It will be understood that the term “substantiallycontinuously” refers to a continuous mode of operation whereby carbonbodies 30 are moved in either a uniform rate or a periodic or step-wisepassage through furnace 10. Carbon bodies 30 are moved “substantiallycontinuously” through the baking process without the need for furnace 10to be shut down and cooled as in prior art in-ground anode bakingfurnaces. The substantially continuous movement includes the periodicstopping of the downward movement of column 32 that is required tounload the lowermost baked carbon body 30 from baking path 12.

The following exemplary configuration of furnace 10 is described as ananode baking furnace. Other carbon articles may be baked in this type offurnace and the inventions described herein are not to be limited toanodes used for aluminum production. Furnace 10 may be used with otherblock-like carbon articles or loose granular carbon articles.

The exemplary carbon baking furnace 10 shown in FIGS. 1 and 2 defines aplurality (twelve in this example) of vertical baking paths 12. Paths 12are defined by a refractory furnace body 40 that is defined by aplurality of interlocking refractory bricks and other refractorymaterials that are partially supported by an external support frame 42that is disposed below and around refractory furnace body 40. Furnace 10is designed to operate at a steady state so interlocking bricks may beused because the bricks are not repeatedly subjected to heating andcooling cycles. Refractory mortar can be used to hold the brickstogether. Refractory furnace body 40 defines baking paths 12, aplurality of fume channels 34 for hot baking gas flow and cooling airflow 36 and a plurality of volatile fume extraction channels 33 forremoving volatiles from furnace 10 upon the initial heating of greenanodes 30. The furnace body 40 defines different heating zonesincluding, from top to bottom, a volatile extraction zone, a bakingzone, and a cooling zone. The zones are defined by the serpentine fumechannels which run substantially perpendicular to and between the bakingpaths and move upwardly from lower areas of the furnace body to higherlevels of the furnace body.

As the carbon anodes 30 pass through furnace 10, they are loaded at aloading zone at the top of furnace 10 and then pass down through avolatile extraction zone (reference numeral 31 FIG. 30) which is heatedin a general range from about 50 degrees C. to 400 degrees C. Volatilessuch as pitch fumes are extracted through holes or volatile extractioninlets 44 in the refractory materials 40 and are moved in the mannerdescribed below. Furnace body 40 defines independent volatile extractionchannels 33 (shown as solid black lines in FIG. 30) that are sandwichedbetween the serpentine baking fume channels 34. Maintaining independentvolatile extraction channels 33 allows the extraction of volatiles to becontrolled and allows the extracted volatile fumes to be selectivelyincinerated. Anodes 30 then pass through a baking or kiln area 37 (FIG.30) where the anodes baked at high temperatures (such as 1200 degreesC.) and then through a cooling zone 38 (FIG. 30) before reaching anunloading zone. Air is drawn into cooling zone 38 through an entrance36A and exhausted at exits 36B. This air may be redirected to be usedwith burners 211. Reference numeral 36C is a damper. Reference numeral39 in FIG. 30 represents locations where removable plugs or dampers areprovided for adding or removing air so that the flue walls can beselectively reconfigured.

Green anodes 30 are positioned at the top of baking paths 12 with adelivery device 50 which may be in the form of the crane 50 depicted inthe drawings. Crane 50 supports anode 30 from its center (at depressionsdefined by the top of the anode) so that each anode 30 may be loweredinto baking path 12 without requiring supports disposed at the sides orunder article 30. If desired, this configuration allows crane 50 to loadanode 30 all the way to the bottom of baking path 12 when furnace 10 isinitially loaded. Anodes 30 also may be loaded from the bottom of eachcolumn. This configuration allows crane 50 to reach into baking path 12to remove anode 30 as needed. A spacer 52 may be positioned on top ofeach anode 30. Spacer 52 may be fabricated from a refractory materialsuch as a ceramic. A super duty fireclay brick material may be used forthe spacers 52 with a density of about (within a range of 5%) 2.27 gramsper cubic centimeter. The material sold under the registered trademarkCLIPPER DP is an exemplary material that may be used to form spacers 52.Spacer 52 may be provided in multiple sections that fit together on topof anode 30. The sections may overlap and have stepped edges or steppedjoints to help spacer 52 fit together. Spacer 52 may include protrusionsto fill the openings on top of the anodes.

In the volatile extraction zone, the fume extraction channels haveinlets 44 defined by the furnace walls that define baking paths 12. Inthe exemplary configuration, each baking path 12 has nine inlets 44 oneach of its longer sides for a total of eighteen inlets 44. The eighteeninlets 44 are disposed in sets of six at three different levels. Othernumbers of inlets and arrangements may be used. For example, the inletsmay be disposed on more or fewer levels and different numbers of inletsmay be used on each level. Each inlet 44 is an opening defined betweenportions of the refractory bricks as shown in FIG. 5A. Using definedinlets 44 provides large openings that limit the available surfaces forthe accumulation of condensed pitch fumes.

Inlets 44 provide fluid communication between baking paths 12 andelongated volatile extraction channels 33 that are in fluidcommunication with a source of reduced pressure (this may be the fanthat moves gases through the entire furnace or a separate fan) thatpulls fumes and volatiles out of the baking paths 12. An alternativeconfiguration connects inlets 44 to the top channels 34 so the volatilesare mixes with the exhaust gases and delivered to an afterburner. Thesevolatile fume channels 33 may be lined with a removable liner 45 (suchas the one shown in FIG. 5B and FIG. 33) that defines a common channelfor removing volatiles from a plurality of inlets 44 with which it isassociated. Liner 45 defines a plurality of inlet slits 47 that arealigned with inlets 44 when liner 45 is installed. Liner 45 alsoincludes an end flange 49 that abuts the exterior of the blocks. Liner45 is removable so that it may be cleaned or replaced. Alternatively,liner 45 can be fixed in place and then cleaned in place by insertingand removing a scrubbing tool. Furnace body 40 defines guides 40A (FIG.33) that help locate liners 45 as they are installed within volatileextraction channels 33. Guides 40A have angled leading ends to directliner 45 toward the sidewall of channel 33.

Alternatively, the removable liner 45 or the volatile fume channelsdefined by the refractory bricks may be segmented so that each inlet 44is in communication with an independently defined and independentlyvalved (reference numeral 41 indicates controllable valves) extractionchannel 43 that allows the flow rate for each inlet 44 to beindependently controlled. A schematic of this configuration is shown inFIG. 5C. This configuration allows the flow rate for each inlet 44 to besubstantially the same regardless of the distance of inlet 44 fromheader 210. This also allows sensors (pressure, temperature, flow rate,and/or chemical sensors) to be used to control flow rate for inlets 44based on real time conditions. For example, a higher flow rate may beapplied to inlets 44 that are experiencing higher levels of volatiles.In another configuration, liner 45 may be segmented to provide theplurality of inlets associated with a single baking path 12 with theirown channel 43.

Inlets 44 are shown in FIG. 5A. Each inlet 44 is substantially largerthan the average size of the sacrificial medium so that pieces ofsacrificial medium will not become wedged in inlets 44. The width andheight of inlets are larger than the width of outlets 102 and may be atleast twice the average particle size of medium and may be more thanfive times the average particle size. Inlets 44 can be the entire heightof one brick course as shown in FIG. 5A with the bottom wall of inlet 44being defined by an upwardly sloping surface 51 with its lowest endnearest the baking path 12 and highest end nearest the volatile fumechannel. Surface 51 is defined by an angled lateral portion ofrefractory brick disposed under inlet 44. The upper wall of inlet 44 isdefined by another brick disposed one or two courses above inlet 44. Theupper wall may be parallel to the bottom wall but does not need to beparallel to allow inlet 44 to function. The upper wall can slope down sothat the top of inlet 44 at baking path 12 is disposed below the top ofthe fume channel or liner 45. This arrangement limits the accumulationof sacrificial medium particles in inlet 44. The sloped configuration ofinlet 44 allows sacrificial medium that enters inlet 44 to move out asthe sacrificial medium in baking path 12 moves down. The sloped bottomsurface prevents particles of sacrificial medium from sitting in inlet44 for long periods of time where they can stick and eventually requireremoval by scraping. The sloped inlets 44 are believed to beself-cleaning because the particles of sacrificial medium entering inlet44 move out when the sacrificial medium within baking path 12 moves downpast inlet 44. The sloped inlets 44 also prevent the sacrificial mediumfrom moving up into the volatile fume extraction channels. The slopedinlets 44 and the extraction liner 45 can be used with a variety offurnaces independent of anode furnaces although the initial heating ofanodes for the aluminum industry is known to create pitch fumes.

As described above, furnace 10 has a volatile extraction zone whereanodes 30 are initially heated and volatiles are driven off intoextraction channels 45 such as those shown in FIGS. 5A, 5B, and 5C. FIG.11 shows the arrangement of six liners 45 and their communication with avolatile extraction header 210. These six liners 45 are used withseventy-two inlets 44 on the sidewalls of baking paths 12. Thearrangement depicted in FIG. 11 is used between rows of baking paths 12.Similar arrangements with only three liners 45 are used on the front andrear ends of furnace 10. The vertical spacing between channels 45depends on the furnace size and the item being baked in the furnace.Header 210 delivers volatiles to the burners 211 as shown in FIG. 12when a first valve 212 is open and a second valve 214 (at the top ofduct 210) is closed. Valves 212 and 214 are remotely controllable todeliver the volatile fumes to either burner 211 or to an afterburner 216(FIG. 1) or a combination of both. Each valve 212 and 214 may be agate-style valve and each has its own actuator to allow the valve to beautomatically and remotely controlled. When first valve 212 is closedand second valve 214 is open, volatile fume is delivered to afterburner216 and this configuration is automatically actuated during an emergencysituation or when burners 211 are off. Afterburner 216 exhausts to astack 218 for delivery to the atmosphere or to further environmentalcontrols. Delivering the extracted volatile fumes to burners 211 reducesthe volatiles that must be burned in an afterburner or delivered to acleaning apparatus before the fumes are exhausted to the atmosphere.Burning the volatile fumes with burners 211 in combination with the fuelfor burners 211 (usually natural gas) requires a high quality pressedand fired refractory brick to be used at the main baking zones offurnace 10 because the bricks must be resistant to the products ofburned volatiles such as alkali. When the volatiles are being introducedto burners 211, furnace 10 is acting as a self-contained incinerator inaddition to a carbon baking furnace.

Burners 211 and the air delivery ducts are mounted to accommodateexpansion and contraction of the refractory bricks of furnace 10. FIG.12 shows each burner 211 mounted to a plenum 220 that accommodatesmovement of the refractory bricks. A plurality of springs 222 are usedbetween the components and frame 42 to create a holding force againstthe bricks while allowing for accommodation of brick movement. The airdelivery system uses similar springs and adjustable plenums toaccommodate movement.

Frame 42 includes a plurality of lower supports 46 that supportrefractory body 40 above the floor 48 on which furnace 10 is supported.Lower supports 46 may be concrete pillars. Lower supports 46 providespace for the unloading of the baked anodes 30. Steel beams may bedisposed on supports 46 with body 40 supported on the beams. A thinlayer of refractory material such as a ceramic fiber may be disposedbetween body 40 and the beams to accommodate expansion and contractionof body 40. An example material is Express-27 Plus. Frame 42 alsosupports a plurality of pressure plates 39 that may be moved toward andaway from body 40. For example, furnace body 40 may be heated to itssteady state temperature and then plates 39 may be moved against theouter surface to provide some lateral support to body 40. As depicted inFIG. 1, plates 39 are disposed between baking paths 12. Plates 12 alsomay be disposed at the corners of body 40. The plates 39 spread theholding force across a plurality of refractory bricks.

After a column is initially loaded and furnace 10 is fired and hasreached steady state, the anode column is slowly lowered in asubstantially continuous manner to bake the anodes. As the column islowered, a new green anode 30 is placed at the top of the column. Theinitial placement of anode 30 is such that anode 30 is disposedintermediate guides 60 (FIG. 4) of which at least one is disposed oneach side of the top of baking path 12 such that anode 30 is centeredabove path 12. The exemplary configuration of guides 60 shown in thedrawings are substantially fixed guide plates. In another configuration,each guide 60 is provided in the form of a roller or a plurality ofrollers. The initial location places the majority of the height of anode30 above the top of baking path 12. As column 32 of anodes 30 is loweredthrough path 12, sacrificial medium such as granular packing coke ispositioned around anode 30 by a sacrificial medium delivery system 64.

In the exemplary configuration of furnace 10, anodes 30 are loaded intothe tops of the baking paths 12 with overhead crane 50 that lowers anode30 directly into the baking path 12. Crane 50 is capable of loweringanode 30 all the way to the bottom of each baking path 12 which is onemethod of initially loading furnace 10. Furnace 10 is initially loadedby creating columns 32 of anodes 30 surrounded by the packing material.The anode columns also may be created working from the bottom of furnaceby pushing successive greens anodes 30 and spacers 52 up into the bakingpaths 12. FIG. 2 depicts ten of the columns loaded (three with spacers52 on top of the anode column 32) and two empty baking paths 12 waitingto be filled. After columns 32 of anodes 30 are established in eachbaking path 12, furnace 10 is started and brought up to its steady stateoperating condition and the anode columns 32 are lowered as describedbelow. When a column 32 is lowered to a level where the column 32 canaccept the next anode 30, crane 50 is directed to pick up the next greenanode 30 and deliver it directly on top of that column 32. Once anode 30is in position and crane 50 releases anode 30, the recesses in the topof anode 30 that are used by crane 50 to grip and move anode 30 arefilled with the packing material and then spacer 52 is placed on top ofanode 30. Spacers 52 may be positioned with crane 50 or an independentsecond swinging crane (not shown) during the process of positioning themfor placement.

Furnace 10 may include sensors that indicate the position of the top ofthe anode columns. The position of the anode column also may bemonitored by the removal of the lower baked anodes. Crane 50 maycommunicate with these sensors to trigger the pickup and delivery of thenext anode to be loaded.

In this configuration, crane 50 lifts the green anodes from the floorlevel and takes them to the top of furnace 10. In another configuration,the green anodes are delivered to the top of furnace 10 with a conveyor.These may be positioned with a crane or dedicated loader for each path.

The next anode 30 is positioned directly on top of the anode column 32by a plurality of upper guides 60 shown in FIGS. 4 and 5. Upper guides60 are passive. Each upper guide 60 is mounted on a guide base 70 andincludes an arm 72 that is cantilevered from guide base 70. A curvedguide foot 74 is carried by the distal end of arm 72 in a position suchthat the straight bottom of guide foot 74 is substantially vertical anddisposed tangential to a portion of the anode column 32. The top ofguide foot 74 is curved or angled back toward guide base 70 (away fromits anode column 32) so that an anode 30 being lowered through guides 60will be guided into the correct position by the upper curved portion ofguide foot 74 in the situation where anode 30 is not perfectly alignedwith anode column 32 by crane 50 or when the dimensions of anode 30 areslightly out of spec. A pair of conical springs 76 are positionedagainst each other and between guide foot 74 and arm 72 to allow theposition of guide foot 74 to automatically adjust. In the exemplaryconfiguration, guide foot 74 is connected to arm 72 with a pair of bolts78 and conical springs 76 are carried on bolts 78 disposed between arm72 and guide foot 74.

A flexible seal 80 defined by a plurality of overlapping brushes 82having metal bristles is positioned at the upper end of each baking path12. The overlapping portions of brushes 82 at their corners may benotched or cut to accommodate the overlap. Seal 80 engages the perimeterof anode 30 as anode 30 drops down through seal 80. Seal 80 is disposedover the top of the sacrificial medium and limits migration of air intothe sacrificial medium.

Each section of seal 80 includes a plurality of metal bristles mountedin a U-channel 84 that is clamped between an L-shaped base mount 86 anda mounting strip 88 positioned over U-channel 84. This configuration isdepicted in FIGS. 9 and 10.

Furnace 10 includes a sacrificial medium delivery system that generallyincludes at least one sacrificial medium storage container and at leastone sacrificial medium conveying assembly that delivers sacrificialmedium from the container to the space around the top of anode column32. The assembly may be a conveyor or a task provided to crane 50. Inthe exemplary configuration of furnace 10, one sacrificial mediumconveyer assembly 64 is disposed on each side of each row of anodes 30such that there are six sacrificial medium conveyors 64 in thisexemplary configuration. Each of the six sacrificial medium conveyors 64is fed by a sacrificial medium hopper 90. Each sacrificial medium hopper90 is filled automatically by a supplier assembly (not shown) ormanually by the person overseeing the operation of furnace 10. Whencrane 50 is used to maintain hopper 90, a container of sacrificialmedium is picked up by the crane from time-to-time and moved over hopper90 wherein an outlet to the container is opened to deliver the medium tohopper 90.

Each sacrificial medium conveyor 64 includes an elongated channel 92 anda sacrificial medium delivery apparatus 94 disposed within channel 92.Delivery apparatus 94 may be the drag chain described herein, a screwconveyor, a vibratory conveyor, or other conveyor used to move granularmaterial along channel 92. The upstream end of channel 92 is loaded withsacrificial medium from hopper 90. The loading of medium from hopper 90to channel 92 is achieved via gravity and controlled with an adjustabledoor 95 as shown in FIG. 7A. Door 95 may be moved up and down relativeto channel 92 to control the amount of medium delivered to channel 92.When in use, door 95 is open to a height that allows the nature angle ofrepose of the medium to be engaged by paddles 100 without overflowingchannel 92 or burying the upstream drive gear 104. Delivery apparatus 94moves the sacrificial medium downstream through channel 92. Deliveryapparatus 94 includes a motor 96 that drives a belt or chain 98 thatcarries paddles 100 disposed within channel 92. Paddles 100 push thesacrificial medium in the downstream direction past a plurality ofoutlets 102 defined by the inner wall of channel 92 disposed adjacentanode column 32. Outlets 102 are disposed under seal 80. In some cases,the inner corners of the brick may be removed to define chutes 103 tohelp the sacrificial medium flow into paths 12 from channel 92. Outlets102 may be about 12.5 to 13 mm tall and about 140 to 160 mm long.

Belt or chain 98 is supported on a drive gear 104 (FIG. 7), and endidler gear 106 (FIG. 8), and at least one intermediate idler gear 108(FIG. 10). Additional intermediate idler gears 108 may be provided asneeded to avoid belt sag. End idler gear 106 is supported on tensionbracket 110 movable by turning tension bolt 112. Paddles 100 areL-shaped sections of metal bolted to belt or chain 98.

Outlets 102 are elongated and spaced apart. A plurality of outlets 102have a length that is roughly four or more times as long as the heightof outlet 102. The height is large enough to accommodate the largestsize of sacrificial medium and the large width minimizes clogged outlets102 while also allowing for uniform distribution of sacrificial mediumalong anodes 30. As shown in FIG. 6, an outlet 102 is disposed at thecorner of anode 30 so that sacrificial medium is distributed to the endsof anodes 30 where the sacrificial medium fills in the ends by way ofgravity at the angle of repose for the sacrificial medium. Openings 102at corners may be larger than the other openings to promote thedistribution of sacrificial medium in these locations.

When assembly 64 is started, the paths 12 closest to hopper 90 receivemost of the sacrificial medium. Once the paths 12 are filled andopenings 102 are filled with medium, paddles 100 will continue pushingthe medium farther downstream until it encounters an opening 102 thatcan receive the medium. This process continues until the last sidewallof the anode farthest from hopper 90 is covered with medium. Sensors 113(FIG. 2) are provided to sense this condition and to turn off motors 96as needed. As the sacrificial medium moves down through the bakingpaths, the sensors 113 are triggered and signal the actuation of motors96 to deliver more medium.

The sacrificial medium also may loaded around the anodes 30 with adispenser that is moved by an overhead crane. One option is using thesame crane 50 that loads the anodes. A bin that carries the sacrificialmedium may be picked up by crane 50 after crane 50 has placed an anode.The bin includes a valved outlet sized to dispense sacrificial medium inthe baking paths 12 around anodes 30. In one configuration, the outletmay be sized to fit entirely around the anode perimeter so that thecrane merely needs to locate the bin above the anode and open the valveto fill the entire space around the anode with sacrificial medium. Inanother configuration, the nozzle is sized to be as long as or longerthan the longer side of the anode so the entire side can be filled withone opening of the valve. In another configuration, the outlet is asmall tube and the crane moves the outlet around the perimeter of theanode while dispensing the sacrificial medium.

In another configuration of furnace 10, bins 90 of sacrificial mediummay be located along the sides of the anode columns. The bins haveoutlets that allow the sacrificial medium stored in the bins to flowinto the space around the anode. The outlets may be controlled withvalves or adjustment plates to control the flow of the packing material.These bins may be reloaded manually, with a dedicated conveyor, or witha crane.

Nitrogen gas may be introduced into channels 92 such that the nitrogenwill migrate down into sacrificial medium around anodes 30. Flooding thesacrificial medium with nitrogen limits the amount of oxygen surroundinganode column 32 and thus limits reactions within the sacrificial medium.A fire suppression system also may be integrated into or just belowchannels 92 to flood the areas around the anode column with a firesuppressant. The nitrogen and the fire suppression system may bedisposed below brushes 82.

The sacrificial medium moves down through baking path 12 with anodes 30and accommodates the movement and size changes of anodes 30 during thebaking process. The sacrificial medium may move at a rate that isdifferent from anodes 30. The sacrificial medium may be moved fasterthan the anodes 30 which accommodates the relatively free movement ofthe anode stack down the baking path regardless of any expansion andcontraction of individual anodes 30.

A lower seal 120 shown in FIGS. 13, 14, and 15 supports the sacrificialmedium and also limits migration of air into the bottom of the bakingpaths 12 through the sacrificial medium. Lower seal 120 is similar toupper seal 80 in that it includes overlapped brushes 82 with metalbristles. In the exemplary configuration, a plurality of stacked brushes82 are used to form seal 120. The ends of the brush bristles are clampedin a U-channel 84 that is received directly in a slot defined by aninner wall 122 of a sacrificial medium removal channel 124. One removalchannel 124 is disposed along each side of each baking path 12 tocontrol the movement of medium through the baking paths 12.

The sacrificial medium is stopped by lower seal 120 and is moved overinner wall 122 into channel 124 between inner wall 122, an outer wall126, and a bottom wall 128 which define the upper portion of channel124. Bottom wall 128 of channel 124 defines openings (FIGS. 14 and 15)which allow the sacrificial medium to drop down into an elongated inlet130 to a sacrificial medium control mechanism 132 which functions as anintermediate channel portion of removal channel 124. Mechanism 132controls the movement of sacrificial medium by removing the sacrificialmedium only as needed by automatically removing the sacrificial mediumfrom the top of a control channel 134. The top of control channel 134 ispositioned above the bottom of elongated inlet 130 such that sacrificialmedium must move upwardly before dropping onto an angled wall 135 of alower gathering channel portion of removal channel 124. The gatheredsacrificial medium is then removed to by way of a chute assembly 136into a collection hopper or is removed by chute assembly 136 to aconveyor that delivers sacrificial medium back to hoppers 90.

Control channel 134 catches the sacrificial medium and prevents it fromsimply falling out of furnace 10 by changing the flow direction of thesacrificial medium. In order to control the movement, control channel134 rocks back and forth on a pivot 138 about which its end panels 140are mounted. The rocking movement pushes the top portions of thesacrificial medium resting in control channel 134 over its edges intothe gathering channel portion below. The material is pushed by the lowerportions of elongated inlet 130 as channel 134 rocks back and forth asindicated by reference arrow 143 in FIG. 14. The other arrows 142 inFIG. 14 depict the movement of the sacrificial medium.

Control channel 134 is driven back and forth by a drive mechanism 144that includes a motor 145 and a push rod 146A which is connected to eachof control channels 134 by linking rods 146B. Linking rods 146B areconnected to tabs that extend through wall 135 as shown in FIGS. 13 and15. Drive mechanism 144 moves rod 146B back and forth to rock each ofcontrol channels 134 to which it is connected. Faster movement of rod146B results in faster movement of the sacrificial medium throughfurnace 10. In the exemplary configuration, drive mechanism 144 includesmotors 145 that drive rods 146A back and forth below the metal beamsthat support refractory body 40. A slot 148 may be defined in lowersupport 46 to accommodate rod 146A (see FIG. 16). Drive rod extensions146B are connected to drive rod 146A and to channel 134 (or to tabs thatextend down from channel 134 as shown in FIG. 13). Drive rod extensions146B transfer to movement of drive rod 146A to control channel 134.Channels 134 may be rocked with their own individual actuators. Pistoncylinders may be used to move rod 146A or to directly rock channel 134back and forth.

Intermediate guides 160 are disposed above seal 120 to ensure anodecolumn 32 is properly positioned for removal from furnace 10.Intermediate guides 160 have a similar structure as upper guides 60 andthe same reference numerals are used to identify these elements ofguides 160. The arms 72 of intermediate guides 160 extend down intosacrificial medium removal channel 124 and may abut bottom wall 128 ofchannel 124.

Chute assembly 136 moves the sacrificial medium out of furnace 10 to alocation where it can be screened and recycled. Chute assembly 136includes a plurality of funnels 162 and 164 disposed around theperimeter of each baking path 12. The longer sides of each baking path12 use a pair of funnels 164 that direct collected medium towards thecorners of the baking path 12. The shorter sides use funnels 162 thatdirect collected medium to the middle of the baking path 12. There arethus six outlets for each baking path 12. The sacrificial medium exitingchannels 124 drops into a funnel 162 or 164 which directs the medium tochannels 170 (see FIG. 16) that allow sacrificial medium to slide downand out of furnace 10 where it is gathered to be used again. Channels170 may be embedded into the furnace supports as shown in FIG. 16 or maybe disposed alongside the supports. Channels 170 may be closed oropen-top. FIG. 16 does not depict grabs 190 but instead shows thesupports for shafts 192. Also, FIG. 16 does not show the chutes thatconnect funnels 162 and 164 to channels 170. For example, a bypass chutedelivers sacrificial medium from funnel 162 beside or around drive rod146A and into channel 170.

Lower guides 180 are disposed below seal 120 and position anode 30 to beheld by the holding mechanism that supports anode column 32 in placewhile the lowermost anode 30 is removed from furnace 10. Lower guides180 have a similar structure as upper guides 60 and the same referencenumerals are used to identify these elements of guides 180.

The holding mechanism includes a plurality grabs 190 which may becurved, toothed holding grabs 190 that pivot downwardly and inwardlyinto opposite sides of the second lowest anode to hold the anode column.The lowest (or first lowest) anode is supported by the screw jack 200 asdescribed below. In the exemplary configuration, two grabs 190 aredisposed on each side of baking path 12 such that four grabs 190 engagethe second lowest anode when the holding mechanism is moved to itsengaged position or its engaged configuration. Each grab 190 is mountedto a drive shaft 192 that is rotated back and forth between engaged anddisengaged positions by a drive mechanism. As shown in FIG. 21, theholding mechanisms disposed at the inner portion of furnace 10 areconnected to their drive mechanisms with bypass drive shafts 191 thatextend behind the grab support structures and are thus offset fromshafts 192 (FIG. 20). In one configuration (FIG. 22), shafts 191 and 192are driven by piston cylinders 196 connected to links 198. In anotherconfiguration (FIG. 23), an actuator motor and gearbox 194 is used todrive grabs 190 between the engaged and disengaged positions. Thesearrangements allow both the inner and outer grabs 190 to be controlledfrom the outer ends of the furnace by extending shafts 191 and 192 outto the furnace ends and locating the drive mechanisms in theselocations.

When the lowermost anode 30 is ready to be removed from column 32, thedrive mechanisms are actuated to move opposed pairs of grabs 190 intoengagement with the second lowermost anode 30. As the lowermost anode 30is moved down, the second lowermost anode 30 starts moving down underthe weight of column 32 causing grabs 190 to continue pivotingdownwardly and inwardly which causes them to bite into the side of thatanode 30 until grabs 190 lock and prevent downward movement of the anodecolumn 32. Column 32 thus stops moving and the lowermost anode 30 isremoved as described below.

To facilitate anodes 30 that are not perfectly square to grabs 190, atleast one grab 190 on each side of baking path 12 is an accommodatinggrab 190 a (FIGS. 25 and 26) that adjusts its position when it initiallyengages the side of the anode 30. The accommodating grab 190 a canadjust its position through an adjustment angle of about five to tendegrees which allows the lateral position of the grab teeth to engage ananode sidewall through a range of about four to eight millimeters.Accommodating grab 190 a includes a spring that forces the grab towardthe anode. Accommodating grab 190 a can thus engage the side of theanode 30 through a range of anode positions. Accommodating grabs 190 amay be disposed directly across from each other or at angles to oneanother across the anode 30. With two grabs 190 a, the totalaccommodation is in the range of eight to sixteen millimeters.

The downward movement of anode column 32 is controlled by an anodecolumn unloading device disposed under the anode column. The unloadingdevice is provided in the form of a screw jack 200 positioned directlyunder column 32 in the exemplary configuration of furnace 10. Screw jack200 is configured to move slowly such as when it is being used to dropanode column 32 down along baking path 12 during the baking of anodes30. Screw jack 200 can also move relatively fast such as when it isremoving the lowermost anode 30 from furnace 10. Screw jack 200maintains its slow movement until grabs 190 are holding column 32. Screwjack 20 then changes to its faster movement and lower the lowermostanode 30 down to a gravity powered passive conveyor 202 which removesthe anode to a removal area 203 (FIG. 17) where a forklift can removethe baked anodes. An advantage of using a screw jack is that it holdsits position during a power interruption. Other devices such ashydraulic lifts may be used.

Another system for holding the anode column is shown in FIG. 29 whereinthe spacer 52 defines notches 250 which allow holding fingers 252 to bedriven between spaced anodes 30 when spacer 52 is aligned with fingers252. Fingers 252 may be drive linearly back and forth with actuators orthey may pivot into notches 250. When fingers 252 are disposed under theanode stack, the lowermost anode can be lowered to the conveyor 202while the anode stack remains held in place. A further configuration forholding column 32 is to use holding plates that press into the side ofthe second lowermost anode. The plates may be driven with hydraulicpressure.

During this process, the anode 30 from the front row 14 of the bakingpath array is removed first and the screw jack 200 remains retracteddown under the conveyor 202 until the anodes from the middle 16 row isremoved and, following the same process, the anode from the back row 18is removed. In an alternate configuration, the back row anode may beremoved from the back of the furnace. This process allows the anodesfrom the middle and back rows to slide down conveyors 202 without beingstopped by the jack screws for the front row of anodes. After anodes 30are removed from all rows 14, 16, and 18, screw jacks 200 are extendedback up to engage columns 32. In order to break the grip of grabs 190,screw jacks 200 lift column 32 up until grabs 190 release or are drivenback to their disengaged positions by actuators 196 or 252. At thattime, screw jack 200 starts moving column 32 downward again until thenew lowermost anode 30 is ready for removal.

This process may be reserved to initially load furnace 10. If loadedfrom the bottom, screw jack 200 lifts an anode 30 to grabs 190 where itis held until pushed up by the next anode 30 being loaded.

As shown in FIGS. 18 and 19, screw jack 200 extends through the centerof conveyor 202. An engagement plate 204 is carried at the top of screwjack 200 to engage anode 30. Plate 204 is supported at five locationsincluding the powered central screw 206 and four corner guides 208.

An alternative conveyor 202 is depicted in FIGS. 27 and 28 whereinconveyor 202 is disposed between anodes 30 such that the anodes arelower to positions beside conveyor 202. Once the baked anode 30 islowered down to the level of conveyor 202, an actuator 230 or 232 pushesor tilts the baked anode 30 onto conveyor 202. Actuator 230 pushes anode30 directly onto conveyor 202 and actuator 232 tilts up and tips anode30 onto conveyor 202 or allows it to slide via gravity.

FIGS. 27 and 28 also show an alternative embodiment for removing thesacrificial medium from the bottom of furnace 10. In this configuration,the sacrificial medium is caught by a chute 240 that delivers thesacrificial medium to a conveyor 242 disposed under conveyor 202.

In the foregoing description, certain terms have been used for brevity,clearness, and understanding. No unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art because suchterms are used for descriptive purposes and are intended to be broadlyconstrued. Moreover, the description and illustration of the furnace isan example and the furnace is not limited to the exact details shown ordescribed. Throughout the description and claims of this specificationthe words “comprise” and “include” as well as variations of those words,such as “comprises,” “includes,” “comprising,” and “including” are notintended to exclude additives, components, integers, or steps.

1. A vertical path carbon baking furnace for baking green carbon articles; the furnace comprising: a refractory material furnace body defining a substantially vertical baking path adapted to receive the green carbon articles; the vertical baking path having a volatile extraction zone disposed above a baking zone; the refractory material furnace body defining a volatile extraction inlet in communication with the substantially vertical baking path; the volatile extraction inlet being disposed in the volatile extraction zone of the baking path; a liner carried within the refractory material furnace body; the liner defining a liner channel in fluid communication with the volatile extraction inlet; the refractory material furnace body defining serpentine baking fume channels disposed on opposite sides of the baking path to receive baking fumes; portions of the serpentine baking fume channels being disposed within the volatile extraction zone; each of the serpentine baking paths has substantially parallel runs within the volatile extraction zone; the refractory material furnace body defining a volatile extraction channel sandwiched between portions of the substantially parallel runs of the baking fume channel; the liner being carried by the refractory material furnace body within the volatile extraction channel; a burner that provides baking fumes to the baking fume channels; and the volatile extraction inlet in fluid communication with the burner through the liner channel such that volatile fumes extracted from the baking path through the volatile extraction inlet and the liner channel can be selectively delivered to the burner for combustion.
 2. A vertical path carbon baking furnace for baking green carbon articles; the furnace comprising: a furnace body defining a substantially vertical baking path adapted to receive the carbon article; the baking path having upper and lower ends; a sacrificial medium delivery system disposed at the top of the baking path; the sacrificial medium delivery system including a pair of channels disposed on opposite sides of the baking path; each of the channels defining outlets adapted to deliver sacrificial medium from the channel to the baking path; and a sacrificial medium conveyor disposed in the channels; the conveyor having movable elements that deliver sacrificial medium to the channel outlets along the length of the channels.
 3. A vertical path carbon baking furnace for baking green carbon articles; the furnace comprising: a furnace body defining a substantially vertical baking path adapted to receive the carbon articles in a stacked column wherein the stacked column has a lowermost article and a second lowermost article; the baking path having upper and lower ends; an unloading device disposed under the baking path to control the movement of the column through the baking path; a holding mechanism associated with the baking path; the holding mechanism having elements that selectively support the second lowermost article independent of the lowermost article; and the holding mechanism including a plurality of grabs that selectively rotate downwardly and inwardly relative to the article from a disengaged position to an engaged position; the plurality of grabs including grabs disposed on opposite sides of the article such that the weight of the article causes the article to be pinched and held by the opposed grabs. 